This invention relates to peristaltic pumps.
In one class of peristaltic pumps such as that disclosed, for example, in U.S. Pat. No. 3,366,071 to Dutler granted Jan. 3, 1963, a plurality of rollers are orbited about a central driving shaft and compress a tube, with the rollers rolling against a bearing surface to control the amount of compression of the flexible tube.
In a prior art unit of this type, the rollers are in the form of cylinders, each having two steps of diameter. The inner step of the roller cylinders is radially compliant, fits within a substantially circular crosssectional compartment and is traction driven by a central axle to follow an orbit along the roughly circular path. The outer step of the roller cylinders extends into a circumferential slot in the roughly circular crosssectional compartment and compresses the flexible tube therein to pump the fluid.
This type of peristaltic pump has several disadvantages such as: (1) it is difficult to machine the radially compliant rollers with sufficient precision; (2) it works best as a single-channel pump and is clumsy to use as a multiple-channel pump; and (3) it is difficult to adjust the pump to different size conduits or for different pumping configurations.
Another type of peristaltic pump includes a plurality of cassettes rigidly holding tubes to rollers and having gearing on the rollers to provide forced backspin for preventing stretch of the tube from the drive of the orbiting rollers, for reducing the tendency of the tube to crawl through the cassette and for reducing pulses due to the stretching. This prior art pump has the disadvantage of being expensive to make with the tolerances necessary for: (1) low fluid pulsation; (2) long tubing life; and (3) pressure capability limited only by the strength of the tubing.
Other prior art peristaltic pumps orbit rollers about a central shaft but do not include a support for the rollers that is independent of the drive and which controls the tube. This type of prior art peristaltic pump has several disdvantages such as: (1) the flow rate and fluid pressure change with temperature and wear; (2) it is difficult to manufacture for precision flow rate and cancellation of fluid pulsation because the cumulative effect of machining tolerances extend from the center of the drive shaft to the rollers, the flexible tube and the fixed support for the tube; and (3) for similar reasons, it is difficult to match a plurality of channels.